Liquid cooled heat sink with cold plate retention mechanism

ABSTRACT

A system for cooling electronic components with a surface having one or more electronic components, including an integrated circuit, mounted thereon. A liquid cooled heat exchanger located in overlying contacting relation with the integrated circuit. A resilient cold plate coupled to the surface so as to be biased by a portion of the liquid cooled heat exchanger thereby providing a forced engagement between the liquid cooled heat exchanger, the integrated circuit, and the resilient cold plate.

This nonprovisional patent application claims priority from provisionalpatent application Ser. No. 60/607,933, filed Sep. 8, 2004, entitledVideo Graphics Card Memory Modules Liquid Cooled Heat Sink Plus LiquidCooling Cold Plate Retention Mechanism, which provisional application isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to thermal management for memorymodules and, more particularly, to a liquid cooled heat sink and coldplate retention mechanism.

BACKGROUND OF THE INVENTION

As the power to be dissipated by semiconductor devices increases withtime, a problem arises: over time the thermal conductivity of theavailable materials becomes too low to conduct the heat from thesemiconductor device to the fins with an acceptably low temperaturedrop. The thermal power density emerging from the semiconductor deviceswill be so high that even copper or silver spreader plates will not beadequate. Compounding this problem is that circuit boards are typicallyhoused in enclosures that are increasingly becoming smaller in size.

For relatively low-power systems, air cooling and heat sink techniquesoften adequately maintain lower operating temperatures to suchelectronic components. Application of printed circuit boards that employhigh power electronic components demanded by such equipment used, oftenrequire liquid cooling to minimize the cooling system size, and heattransfer medium required transmitting larger amount of heat rate usingrelatively smaller size cooling system. Several different liquid-coolingmethods have been proposed in the field of cooling high powerdissipating electronic components mounted on printed circuit boards. Atypical processor board can contain a multiplicity of CPU modules withassociated cache memory, ASICs, and DC—DC converters. The total powerdissipation from a similarly configured board can reach more than 600 W.Similar components can exist on each side of a board. Withmicroprocessor power dissipation continuing to increase while the spaceavailable for a thermal solution decreases, it becomes necessary toimprove heat dissipation by the CPU and associated components. One suchimprovement is a single-phase forced-liquid cooling system.

The primary components of a single-phase forced-liquid cooling systemare a pump, a heat exchanger, a liquid-cooled cold plate and someassociated tubing required to interconnect the components and put themin fluid communication (i.e., provide passageways and/or orifices forfluid to travel between the components). Heat is dissipated by themicroprocessor, and/or other power consuming component, and transferredto the liquid circulating through the cold plate, with which thecomponent is in intimate contact. The liquid increases in temperaturewithout changing its phase as it absorbs heat. The liquid is then movedto a heat exchanger, via the pump, where the heat is transferred toambient air, resulting in a reduction in temperature of the liquid. Thecycle is repeated when the liquid re-enters the cold plate. One of themore popular liquid-cooling mechanisms employs an aluminum coverassembly that mounts to a circuit board in overlaying close-fittingrelationship to the surface-mounted electronics. This kind of coolingapparatus is commonly referred to as a cold plate.

Conventional cold plates typically comprise a relatively flat thermallyconductive body formed with an engagement surface that closely mirrorsthe surface configuration or topology of the circuit board. An internalcooling channel is formed in the plate to circulate cooling fluidthrough the body and draw heat away from the cold plate duringoperation. The plate mounts to the circuit board using separatemechanical hardware, e.g., spring loaded clips and the like, with therespective electronic components often nested in correspondingclose-fitting recesses. While conventional cold plates offer significantcooling advantages for printed circuit boards, as compared to air-cooledsystems, some of the drawbacks involve cost and reliability. Typically,the costs associated with cold plates often reflect long lead times andcomplex manufacturing operations, which most often may lead to lowerreliability. Consequently the expense to employ a traditional cold platesystem and its associated mounting hardware, coupled with reliabilityissues in a printed circuit board environment, is often undesirably highcost and lower reliability.

In an effort to address these problems, those skilled in the art haveadvanced many proposals for design and manufacturing cold plates. Forexample, in U.S. Pat. No. 6,305,463, issued to Salmonson, discloses acold plate that provides air or liquid cooling for a computer circuitmodule and has at least one mounting plate with a board mounting surfaceon one side for carrying a printed circuit board assembly and a coolingsurface located on the other side. A cover is disposed parallel to andspaced apart from the mounting plate with a cooling chamber definedbetween the two. U.S. Pat. No. 6,587,343 issued to Novotny, et al.,discloses a water-cooled system and method for cooling electroniccomponents. The system includes a surface with at least one electroniccomponent coupled to the surface, where the at least one electroniccomponent includes an integrated circuit. A closed-loop fluidic circuitis coupled to the surface for removing heat from the integrated circuit.The closed-loop fluidic circuit includes a heat exchanger. U.S. Pat. No.5,050,037, issued to Yamamoto, et al., discloses a printed circuit boardassembly having a printed circuit board mounted, on both faces with heatgenerative electronic circuit components, such as integrated circuitchips, and a pair of liquid-cooling modules arranged on both sides ofthe printed circuit board. Each of the liquid-cooling modules isprovided with a liquid cooling plate having liquid coolant supply headsand a plurality of resilient heat transfer units held by theliquid-cooling plate and arranged in compressive contact with theelectronic circuit components on both faces of the printed circuitboard.

What is needed and has been heretofore unavailable is ahigh-performance, cost-effective cold plate configuration that lendsitself to a high level of manufacturability, and a method thatimplements straightforward design and fabrication steps to minimizecosts and production delays, which in turn simplifies the design of thecooling system, and its components. The cold plate of the presentinvention satisfies these needs.

SUMMARY OF THE INVENTION

The present invention provides a system for cooling electroniccomponents with a surface having one or more electronic components,including an integrated circuit, mounted thereon. A liquid cooled heatexchanger located in overlying contacting relation with the integratedcircuit. A resilient cold plate coupled to the surface so as to bebiased by a portion of the liquid cooled heat exchanger therebyproviding a forced or fully loaded engagement between the liquid cooledheat exchanger, the integrated circuit, and the resilient cold plate.

In another embodiment of the invention, a system for cooling electroniccomponents is provided that includes a surface, e.g., the surface of aprinted wiring board, with one or more electronic components, includingan integrated circuit, mounted on the surface. A liquid cooled heatexchanger is located in overlying contacting relation with theintegrated circuit. A resilient cold plate is coupled to the surface inoverlying contacting relation with the one or more electronic componentsand so as to be biased by a portion of the liquid cooled heat exchangerthereby providing a forced engagement between the liquid cooled heatexchanger, the one or more electronic components, and the resilient coldplate.

In a further embodiment of the present invention, a system for coolingelectronics is provided having a first surface and a second surface,e.g., the top and bottom surfaces of a printed wiring board, with one ormore electronic components including an integrated circuit mounted on atleast the first surface. A liquid cooled heat exchanger is located inoverlying contacting relation with the integrated circuit. A firstresilient cold plate is coupled to the first surface in overlyingcontacting relation with the one or more electronic components and so asto be biased by a portion of the liquid cooled heat exchanger therebyproviding a forced engagement between the liquid cooled heat exchanger,the one or more electronic components, and the first resilient coldplate. A second resilient cold plate coupled to the second surface andthe first resilient cold plate so s to provide additional spring forceto the system and thereby to enhance thermal transfer.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bemore fully disclosed in, or rendered obvious by, the following detaileddescription of the preferred embodiment of the invention, which is to beconsidered together with the accompanying drawings wherein like numbersrefer to like parts and further wherein:

FIG. 1 is a perspective view of a system for cooling electroniccomponents formed in accordance with one embodiment of the presentinvention;

FIG. 2 is a perspective view of a liquid cooled heat exchanger;

FIG. 3 is a cross-sectional view of the liquid cooled heat exchangershown in FIG. 2;

FIG. 4 is another cross-sectional view of the liquid cooled heatexchanger shown in FIG. 2;

FIG. 5 is an exploded perspective view of the liquid cooled heatexchanger shown in FIG. 2;

FIG. 6 is an exploded cross-sectional view of the liquid cooled heatexchanger shown in FIG. 2;

FIG. 7 is an exploded perspective view of a system for coolingelectronic components formed in accordance with one embodiment of thepresent invention;

FIG. 8 is an assembled view of the system for cooling electroniccomponents shown in FIG. 7;

FIG. 9 is an exploded perspective view of a system for coolingelectronic components formed in accordance with an alternativeembodiment of the present invention; and

FIG. 10 is an exploded perspective view of another embodiment of asystem for cooling electronic components formed in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This description of preferred embodiments is intended to be read inconnection with the accompanying drawings, which are to be consideredpart of the entire written description of this invention. The drawingfigures are not necessarily to scale and certain features of theinvention may be shown exaggerated in scale or in somewhat schematicform in the interest of clarity and conciseness. In the description,relative terms such as “horizontal,” “vertical,” “up,” “down,” “top” and“bottom” as well as derivatives thereof (e.g., “horizontally,”“downwardly,” “upwardly,” etc.) should be construed to refer to theorientation as then described or as shown in the drawing figure underdiscussion. These relative terms are for convenience of description andnormally are not intended to require a particular orientation. Termsincluding “inwardly” versus “outwardly,” “longitudinal” versus “lateral”and the like are to be interpreted relative to one another or relativeto an axis of elongation, or an axis or center of rotation, asappropriate. Terms concerning attachments, coupling and the like, suchas “connected” and “interconnected,” refer to a relationship whereinstructures are secured or attached to one another either directly orindirectly through intervening structures, as well as both movable orrigid attachments or relationships, unless expressly describedotherwise. The term “operatively connected” is such an attachment,coupling or connection that allows the pertinent structures to operateas intended by virtue of that relationship. In the claims,means-plus-function clauses, if used, are intended to cover thestructures described, suggested, or rendered obvious by the writtendescription or drawings for performing the recited function, includingnot only structural equivalents but also equivalent structures.

Referring to FIGS. 1 and 7–9, a thermal management system 2 formed inaccordance with the present invention comprises a liquid cooled heatsink 4 and at least one cold plate 6 that acts not only to distributethermal energy within the system, but also to retain liquid cooled heatsink 4 in intimate thermal engagement with a heat generating device 10(FIGS. 1 and 7). More particularly, liquid cooled heat sink 4 comprisesa base plate 12, a lid 14, a first conduit 16 and a second conduit 17. Aplurality of fins 20 project outwardly from a top surface of base plate12, and are often arranged in mutually parallel relation to one another.End ones of fins 20 include a radiused outer surface 22. Plurality offins 20 have a length and width that is less than the length and widthof base plate 12 so that a circumferential portion of base plate 12forms a flange 25 that extends outwardly from all sides of plurality offins 20.

Lid 14 includes a central depression 29 defined by a circumferentialwall 30 that is bounded by a central top wall 32. Two through-bores33,34 are defined by top wall 32 in spaced apart relation to oneanother. A circumferential flange 37 extends outwardly from all sides oflid 14 and away from the central depression 29. Lid 14 is assembled tobase plate 12 so that plurality of fins 20 are housed within the centraldepression formed in lid 14, with a first manifold 40 and a secondmanifold 42 defined between circumferential wall 30 and the ends ofplurality of fins 20. In this construction, through-bore 33 is locatedabove first manifold 40 and through-bore 34 is located above secondmanifold 42, with first conduit 16 assembled in fluid communication withthrough-bore 33 and second conduit 17 assembled in fluid communicationwith through-bore 34. As a result, a cooling fluid (not shown) may beforced through one of the conduits, through plurality of fins 20 and outthe other conduit so as to effect heat transfer from liquid cooled heatsink 4.

Referring to FIGS. 7–9, cold plate 6 is formed from a sheet of thermallyconductive, resilient metal that has a top surface 45, a bottom surface48, an opening 50 defined by a peripheral edge 51 through its thickness,and at least one depression 53. Cold plate 6 preferably possesses springcharacteristics that allow for the storage of elastic energy when aportion of the plate is biased or loaded, i.e., deflected in aspring-like fashion so that a force or load is exerted by cold plate 6in response to the deflection. This spring-like response to engagementwith other structures, e.g., flange 25 of base 12 of liquid cooled heatsink 4, allows for improved thermal conduction across the interface atthe region of contact. In particular, opening 50 of cold plate 6 issized so as not to receive the outer portion of top wall 32 of lid 14and a portion of its entire circumferential wall 30, but instead flange25 of base plate 12 or circumferential flange 37 of lid 14. One or moredepressions 53 are often formed as one or more deep draws in top surface45 of cold plate 6 that form prominences 55 on bottom surface 48.Depressions 53 (like depression 29 defined in lid 14) may be formed byseveral alternative manufacturing methods including, but not limited tostamping, machining, and casting, etc.

Thermal management system 2 is typically used in conjunction with atleast one printed wiring board, e.g., a videographics processing card75, having a processing unit 77 positioned on a top surface 79 ofprinted wiring card 75, with one or more other semiconductor devices,e.g., graphics memory modules 81, distributed around the perimeter ofprocessing unit 77. Thermal management system 2 is assembled tovideographics processing card 75 by positioning liquid-cooled heat sink4 in overlying thermal engagement with the top surface of processingunit 77. In this arrangement, lid 14 and conduits 16, 17 stand proud ofsurface 79 and processing unit 77. In this way, the bottom surface ofbase plate 12 is disposed in intimate thermal communication with the topsurface of processing unit 77.

Once in this position, at least one cold plate 6 is positioned inconfronting relation to top surface 79 of videographics processing card75 such that opening 50 is arranged in coaxial relation withliquid-cooled heat sink 4. In this position, bottom surface 48 onprominence 55 is disposed in confronting spaced relation to peripheralsemiconductor devices 81 (FIG. 10). To complete assembly, cold plate 6is moved toward videographics processing card 75 such that conduits 16and 17 along with the top portion of lid 14 and top wall 32 pass throughopening 50. Cold plate 6 moves toward videographics processing card 75until the portion of bottom surface 48 that is adjacent to peripheraledge 51 defining opening 50 engages flange 25 of base plate 12. At thesame time, bottom surface 48 on prominences 55 engage the top surfacesof each of the peripheral semiconductor devices 81. It is oftenpreferable to deposit a thermal interface material, e.g., thermal greaseor sheet of thermally conductive material, or the like, on one or bothof the thermally engaging surfaces to improve thermal transfer acrossthe interface, and to accommodate the varying heights of electroniccomponents located on videographics processing card 75. Thermalmanagement system 2 is then clamped to videographics processing card 75by conventional fasteners, e.g., threaded bolt or screw fasteners 76, ofthe type well-known in the art. Very often, a second cold plate 6 isarranged in confronting relation on a bottom surface of videographicsprocessing card 75 and is clamped to printed wiring board 75 by the samefasteners used to clamp the top cold plate 6.

As a result of this construction, that portion of cold plate 6 thatengages flange 25 of base plate 12 deflects, thereby storing elasticenergy and providing a contact force operative against flange 25. Inthis way, an intimate thermal engagement is maintained between coldplate 6 and base plate 12 of liquid-cooled heat sink 4 so as to enhancethermal transfer, while at the same time, acting as a retentionmechanism for maintaining liquid-cooled heat sink 4 in position andcontact with processing unit 77. At the same time, prominences 55 areforced against peripheral semiconductor devices 81 by the same storedelastic energy generated by fasteners. As a result, cold plate 6 is alsomaintained in intimate thermal engagement with each of the peripheralsemiconductor devices, whose thermal energy is transferred, viaconduction, through cold plate 6 to flange 25 and thereby to pluralityof fins 20 to be dissipated as cooling fluid washes across plurality offins 20 from manifold 40 to manifold 42. In one embodiment of theinvention, a substantially U-shaped plurality of depressions 54 aredisposed in cold plate 6 that each positionally correspond to theposition of a heat generating device 81 located on videographicsprocessing card 75.

It is to be understood that the present invention is by no means limitedonly to the particular constructions herein disclosed and shown in thedrawings, but also comprises any modifications or equivalents within thescope of the claims.

1. A system for cooling electronic components, said system comprising: asurface; one or more electronic components including an integratedcircuit mounted on said surface; a liquid cooled heat exchanger locatedin overlying contacting relation with said integrated circuit; and aresilient cold plate coupled to said surface so as to be biased by aportion of said liquid cooled heat exchanger thereby providing a loadedengagement between said liquid cooled heat exchanger, said integratedcircuit, and said resilient cold plate.
 2. A system according to claim 1wherein said liquid cooled heat exchanger includes a base plate having aplurality of fins projecting outwardly from a top surface.
 3. A systemaccording to claim 2 wherein said plurality of fins are arranged inmutually parallel relation to one another.
 4. A system according toclaim 2 wherein end ones of said fins include a radiused outer surface.5. A system according to claim 2 wherein said plurality of fins have alength and width that is less than a length and a width of said baseplate so that a circumferential portion of said base plate forms aflange that extends outwardly from all sides of said plurality of fins.6. A system according to claim 2 wherein said liquid cooled heatexchanger includes a lid positioned in overlying relation to said baseplate, and that includes a first conduit and a second conduit.
 7. Asystem according to claim 6 wherein said lid includes a centraldepression defined by a circumferential wall that is bounded by acentral top wall.
 8. A system according to claim 7 wherein said liddefines two through-bores in said top wall that are arranged in spacedapart relation to one another.
 9. A system according to claim 7 whereinsaid lid includes a circumferential flange that extends outwardly fromall sides of said lid and away from said central depression.
 10. Asystem according to claim 6 wherein said lid is assembled to said baseplate so that said plurality of fins are located within a centraldepression defined by a circumferential wall that is bounded by acentral top wall of said lid.
 11. A system according to claim 10 whereinsaid lid, said base plate and said fins define a first manifold and asecond manifold.
 12. A system according to claim 2 wherein said coldplate is formed from a sheet of thermally conductive, resilient metalhaving a top surface, a bottom surface, an opening defined by aperipheral edge through a thickness, and at least one depression.
 13. Asystem according to claim 1 wherein said cold plate stores energy whendeflected in a spring-like fashion so that a force or load is exerted bysaid cold plate in response to said deflection.
 14. A system accordingto claim 12 wherein said plurality of fins have a length and width thatis less than a length and a width of said base plate so that acircumferential portion of said base plate forms a flange that extendsoutwardly from all sides of said plurality of fins and deflects saidcold plate in a spring-like fashion.
 15. A system according to claim 1wherein said resilient cold plate includes at least one depression thatis formed in a top surface so as to define a prominence protruding froma bottom surface.
 16. A system according to claim 1 wherein said surfaceforms a portion of a printed wiring board.
 17. A system according toclaim 1 wherein said one or more electronic components comprise graphicsmemory modules distributed around a perimeter of said integratedcircuit.
 18. A system according to claim 1 wherein said resilient coldplate includes a plurality of depressions that are formed in a topsurface so as to define a plurality of prominences protruding from abottom surface.
 19. A system for cooling electronic components, saidsystem comprising: a surface; a plurality of electronic componentsincluding an integrated circuit mounted on said surface; a liquid cooledheat exchanger located in overlying contacting relation with saidintegrated circuit; and a resilient cold plate coupled to said surfacein overlying contacting relation with said electronic components and soas to be biased by a portion of said liquid cooled heat exchangerthereby providing a spring-loaded engagement between said liquid cooledheat exchanger, said electronic components, and said resilient coldplate.
 20. A system for cooling electronic components, said systemcomprising: a first surface and a second surface; one or more electroniccomponents including an integrated circuit mounted on at least saidfirst surface; a liquid cooled heat exchanger located in overlyingcontacting relation with said integrated circuit; a first resilient coldplate coupled to said first surface in overlying contacting relationwith said one or more electronic components and so as to be biased by aportion of said liquid cooled heat exchanger thereby providing a forcedengagement between said liquid cooled heat exchanger, said one or moreelectronic components, and said first resilient cold plate; and a secondresilient cold plate coupled to said second surface and said firstresilient cold plate.
 21. A system for cooling electronic components,said system comprising: a surface; one or more electronic componentsincluding at least one integrated circuit mounted on said surface; atleast one liquid cooled heat exchanger located in overlying contactingrelation with said at least one integrated circuit; and at least oneresilient cold plate coupled to said surface so as to be biased by aportion of said at least one liquid cooled heat exchanger therebyproviding a loaded engagement between said at least one liquid cooledheat exchanger, said at least one integrated circuit, and said at leastone resilient cold plate.